Process for extracting silver from ore.



.water gas,

, UNITED STATES PATENT OFFICE.

MAB'IINUS H. GABON, 0F WEL'I'EVREDEN, JAVA, DUTCH EAST INDIES, ASSIGNOR '10 RESEARCH CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PROCESS FOR EXTRACTING SILVER FROM ORE.

No Drawing.

To all whom it may concern:

Be it known that I, MAR'rINUs HENDRIG'US- OAnoN, residing at Welte'vreden, Java, Dutch East Indies, have invented certain new and useful Improvements in Processes for Extracting Silver from Ore; and I hereby declare the following to be a full, clear, and exact description of the invention.

This invention is an improvement upon the process formin' the subject of my Patent No. 1,232,216, date July 3, 1917. As stated in my said patent, it is generally known that with certain kinds of ore containing silver, or silver and gold in addition to a relatively high percentage of manganese dioxid (especially oxidation ore) the amalgamation and cyanidation processes result in a very unsatisfactory silver extraction. This low silver extraction is due to the presence of manganese dioxid, this substance apparently forming insoluble double oxid compounds with silver, or otherwise being associated in such a way as to prevent normal action of mercury'or cyanid on the said silver compounds.i

The object of the present invention is to provide an improved process by which this objection is overcome. In this process, the ore after being crushed is first su jected to a reducing roast, by means of roducer gas, wood gas or any ot er generator gas or reducing agent, and this may be done either by directly heating the ore in this reducing atmosphere, or by first heating the ore to the proper temperature, by which a part of the oxygen of the MnO is liberated by disass'ociation, after which it must be reduced by the gases to MnO. The principal thing in this reduction by means of CO,H,, (C H etc., is that MnO should be completely reduced to MnO, all the insoluble silver compounds simultaneously being reduced to metallic silver. The temperature at which a complete reduction to MnO and metallic silver is obtained may vary. I prefer a temerature between 600 C. and 800 C. accordmg to the nature of the ore. If the temperature is increased above 800 C. up to 1000 C. or still higher, extraction by amalgama' tion will be increased considerably but not the extraction by cyanid. In some cases even temperatures below 600 C. may'prove to be sufiicient, say down to 350 C. After the said complete reduction to MnO and Agit Specification of Letters Patent. Patnted Mar, 25, 1919, I I Application filed July 16, 1917. Serial No. 180,834.

is very important to prevent reoxidation of the MnO, as this lowest oxid of manganese, when still hot, is very liable to take up oxygen, passing into higher oxid compounds of manganese, which associate again with the newly formed fine silver particles and thus form insoluble silver manganese compounds.

Hence this reoxidation must be prevented and this may be obtained by cooling the ore completely in reducing gas, or by coolingthe hot ore suddenly in water, out of contact with a1r,or in any other way which excludes oxygen from access to the hot ore.

After the aforesaid treatment, the refractory manganese silver ore is changed into a free milling silver ore and any suitable process for the extraction of the silver may be used.

To sum up, my present invention comprises an improvement in the method of extracting silver from ore containing manganese dioxid in addition to silver or silver and gold, said improvement consisting in (a) A complete reduction of the MnO and the insoluble silver compounds to MnO' and metallic silver by means of a reducing roast at suitable temperatures. and Y (b) A cooling of the hot reduced ore'in such a way as to prevent reoxidation of the newly formed MnO and Ag. This may be effected by cooling the ore in reducing gas or in water, so as to prevent access of a1r, or in any other suitable way which prevents reoxidation. After said preparatory treatment the refractory manganese silver ore is changed into a free milling silver ore and may be extracted by amalgamation, cyanidation, flotation or any other suitable method.

I claim:

1. Process of recovering values from ores containing manganese dioxid, comprising ducing conditions, and recovering the values from the reduced ore by methods applicable to free-milling ores.

containin manganese. oxid, comprising heating t e ore to a temperature sufiicient to,

eliminate a ortion of the oxygenof the 5 manganese dloxid, subjectin the heated ore to the action of a gaseous re ucing agent to effect a further reduction thereof, cooling tions and recoverin the values from the reduced ore by metho s applicable to free-mill in ores.

ntestimony whereof I have signed m name to this specification.

- MARTINUS H. GABON. 

